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United States Patent |
5,535,767
|
Schnatzmeyer
,   et al.
|
July 16, 1996
|
Remotely actuated adjustable choke valve and method for using same
Abstract
A remotely-adjustable valve employable in an enhanced-lift recovery system
and a method of adjusting the same. The valve comprises: (1) an elongated
valve body having a process fluid inlet and a process fluid outlet, (2) an
elongated valve stem disposed within the valve body for axial displacement
relative thereto to adjust a rate of process fluid flow between the fluid
inlet and the fluid outlet as a function of a relative axial position of
the valve stem with respect to the valve body and (3) a cam disposed
within the valve body and coupling the valve body and the valve stem, the
cam providing a plurality of axial displacement positions thereon to place
the valve stem at a selected one of a plurality of relative axial
positions with respect to the valve body, the valve body having a control
fluid pressure port for allowing a control fluid pressure to be introduced
into and released from the valve to reciprocate the valve stem axially
with respect to the valve body between cocked and set positions, the cam
moving from a first axial displacement position to a second axial
displacement position as the valve stem is reciprocated, a difference
between the first and second axial displacement positions thereby causing
an adjustment of the rate of process fluid flow between the fluid inlet
and the fluid outlet.
Inventors:
|
Schnatzmeyer; Mark A. (Lewisville, TX);
Pearce; Joseph L. (Dallas, TX)
|
Assignee:
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Halliburton Company (Houston, TX)
|
Appl. No.:
|
404211 |
Filed:
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March 14, 1995 |
Current U.S. Class: |
137/1; 137/155; 417/109 |
Intern'l Class: |
F04F 001/20 |
Field of Search: |
137/1,155
417/109
|
References Cited
U.S. Patent Documents
2366175 | Jan., 1945 | Boynton | 137/155.
|
2368406 | Jan., 1945 | Boynton | 137/155.
|
2371220 | Mar., 1945 | Boynton | 417/109.
|
3427989 | Feb., 1969 | Bostock et al.
| |
5176164 | Jan., 1993 | Boyle | 137/155.
|
Other References
Guide to Otis Versa-Trieve Packers, 1988, author unknown.
|
Primary Examiner: Michalsky; Gerald A.
Attorney, Agent or Firm: Imwalle; William M., Gaines; Charles W.
Claims
What is claimed:
1. A remotely-adjustable valve employable in an enhanced-lift recovery
system, comprising:
an elongated valve body having a process fluid inlet and a process fluid
outlet;
an elongated valve stem disposed within said valve body for axial
displacement relative thereto to adjust a rate of process fluid flow
between said fluid inlet and said fluid outlet as a function of a relative
axial position of said valve stem with respect to said valve body;
a cam disposed within said valve body and coupling said valve body and said
valve stem, said cam providing a plurality of axial displacement positions
thereon to place said valve stem at a selected one of a plurality of
relative axial positions with respect to said valve body, said valve body
having a control fluid pressure port for allowing a control fluid pressure
to be introduced into and released from said valve to reciprocate said
valve stem axially with respect to said valve body between cocked and set
positions, said cam moving from a first axial displacement position to a
second axial displacement position as said valve stem is reciprocated, a
difference between said first and second axial displacement positions
thereby causing an adjustment of said rate of process fluid flow between
said fluid inlet and said fluid outlet.
2. The valve as recited in claim 1 wherein said cam is rotatable and
provided with a J-slot about a circumference thereof, said J-slot adapted
to receive a follower therein to govern said relative axial position of
said valve stem with respect to said valve body, said J-slot having a
plurality of intermediate passages coupling said plurality of axial
displacement positions.
3. The valve as recited in claim 1 further comprising a follower coupling
said valve stem to said valve body.
4. The valve as recited in claim 1 wherein said valve stem comprises a
differential piston, said differential piston being reciprocable within a
chamber of said valve body and defining a control fluid chamber about said
differential piston, introduction of said control fluid pressure into said
control fluid chamber causing said valve stem to move into a cocked
position.
5. The valve as recited in claim 1 wherein said valve body and said valve
stem define a compensation pressure chamber at an end distal to said
process fluid outlet, said valve body including a compensation pressure
port allowing fluid communication between said compensation pressure
chamber and an environment surrounding said distal end.
6. The valve as recited in claim 1 wherein said valve body and said valve
stem define a compensation pressure chamber at an end distal to said
process fluid outlet, said valve stem including a compensation pressure
port allowing fluid communication between said compensation pressure
chamber and an environment surrounding said process fluid inlet.
7. The valve as recited in claim 1 wherein said cam provides at more than
one axial displacement positions thereon.
8. The valve as recited in claim 1 wherein said cam provides an axial
displacement position in which said valve stem closes said valve.
9. The valve as recited in claim 1 wherein said valve body is operable to
be disposed within a side pocket mandrel associated with a well flow
conductor.
10. The valve as recited in claim 1 further comprising a spring biasing
said valve stem toward a closed position with respect to said valve body.
11. The valve as recited in claim 1 further comprising a remote source of
controllable hydraulic pressure coupled to said control fluid pressure
port, said remote source capable of establishing and interrupting a
prescribed pressure to reciprocate said valve stem within said valve body.
12. The valve as recited in claim 1 further comprising a sensor for
relaying data concerning said valve to a remote location, said sensor
selected from the group consisting of:
a tubing pressure transducer, and
a valve stem axial displacement transducer.
13. The valve as recited in claim 1 wherein said process fluid inlet
communicates with a casing of a subterranean well.
14. The valve as recited in claim 1 wherein said process fluid outlet
communicates with production tubing located within a casing of a
subterranean well.
15. The valve as recited in claim 1 further comprising a check valve to
prevent substantial process fluid flow from said process fluid outlet to
said process fluid inlet.
16. The valve as recited in claim 1 wherein said control fluid pressure is
produced by a control fluid selected from the group consisting of
hydraulic fluid and gas.
17. The valve as recited in claim 1 wherein first and second annular seals
disposed about said valve body cooperate with a mandrel surrounding said
valve body to create an annular chamber to receive a control fluid for
introduction into said valve via said control fluid pressure port.
18. The valve as recited in claim 1 further comprising a running/pulling
tool coupled to an end of said valve body distal to said process fluid
outlet, said valve removably locatable in a mandrel within a subterranean
well.
19. The valve as recited in claim 1 wherein said valve is located in a side
pocket mandrel associated with production tubing in a subterranean well, a
casing surrounding said production tubing adapted to receive a process
fluid and transfer said process fluid to within said production tubing at
said rate of process fluid flow via said valve.
20. A method of remotely adjusting a valve employable in an enhanced-lift
recovery system, comprising the steps of:
introducing a control fluid pressure into a control fluid pressure port in
an elongated valve body, said valve body having a process fluid inlet and
a process fluid outlet;
axially displacing an elongated valve stem disposed within said valve body
from a first set position to a cocked position, said valve stem axially
displaceable relative to said valve body to adjust a rate of process fluid
flow between said fluid inlet and said fluid outlet as a function of a
relative axial position of said valve stem with respect to said valve
body;
moving a cam from a first axial displacement position to an intermediate
position with said valve stem, said cam disposed within said valve body
and coupling said valve body and said valve stem, said cam providing a
plurality of axial displacement positions thereon to place said valve stem
at a selected one of a plurality of relative axial positions with respect
to said valve body; and
releasing said control fluid pressure, said valve stem moving said cam from
said intermediate position to a second axial displacement position, a
difference in said first and second axial displacement positions thereby
causing an adjustment of said rate of process fluid flow between said
fluid inlet and said fluid outlet.
21. The method as recited in claim 20 wherein said step of moving comprises
the step of rotating said cam, said cam provided with a J-slot about a
circumference thereof, said J-slot adapted to receive a follower therein
to govern said relative axial position of said valve stem with respect to
said valve body, said J-slot having a plurality of intermediate passages
coupling said plurality of axial displacement positions.
22. The method as recited in claim 20 wherein said step of moving comprises
the step of sliding, with respect to said cam, a follower coupling said
valve body to said cam.
23. The method as recited in claim 20 wherein said valve stem comprises a
differential piston, said differential piston being reciprocable within a
chamber of said valve body and defining a control fluid chamber about said
differential piston, said step of axially displacing comprising the step
of introducing of said control fluid pressure into said control fluid
chamber, thereby causing said valve stem to move into a cocked position.
24. The method as recited in claim 20 wherein said valve body and said
valve stem define a compensation pressure chamber at an end distal to said
process fluid outlet, said method further comprising the step of allowing
fluid communication, via a compensation pressure port associated with said
valve body, between said compensation pressure chamber and an environment
surrounding said distal end.
25. The method as recited in claim 20 wherein said valve body and said
valve stem define a compensation pressure chamber at an end distal to said
process fluid outlet, said method further comprising the step of allowing
fluid communication, via a compensation pressure port associated with said
valve stem, between said compensation pressure chamber and an environment
surrounding said process fluid inlet.
26. The method as recited in claim 20 wherein said cam provides at least
three axial displacement positions thereon.
27. The method as recited in claim 20 wherein said cam provides an axial
displacement position in which said valve stem closes said valve, said
method further comprising the step of closing said valve with said valve
stem.
28. The method as recited in claim 20 further comprising the step of
disposing said valve within a side pocket mandrel associated with a well
flow conductor.
29. The method as recited in claim 20 further comprising the step of
biasing said valve stem toward a closed position with respect to said
valve body with a spring.
30. The method as recited in claim 20 further comprising the step of
establishing and interrupting a prescribed pressure to reciprocate said
valve stem within said valve body with a remote source of controllable
hydraulic pressure coupled to said control fluid pressure port.
31. The method as recited in claim 20 further comprising the step of
relaying data concerning said valve from a sensor to a remote location,
said sensor selected from the group consisting of:
a tubing pressure transducer, and
a valve stem axial displacement transducer.
32. The method as recited in claim 20 further comprising the step of
communicating fluid between said process fluid inlet and a casing of a
subterranean well.
33. The method as recited in claim 20 further comprising the step of
communicating fluid between said process fluid outlet and production
tubing located within a casing of a subterranean well.
34. The method as recited in claim 20 further comprising the step of
preventing substantial process fluid flow from said process fluid outlet
to said process fluid inlet with a check valve.
35. The method as recited in claim 20 wherein said control fluid pressure
is produced by a control fluid selected from the group consisting of
hydraulic fluid and gas.
36. The method as recited in claim 20 wherein first and second annular
seals disposed about said valve body cooperate with a mandrel surrounding
said valve body to create an annular chamber, said method further
comprising the step of receiving a control fluid into said annular chamber
for introduction into said valve via said control fluid pressure port.
37. The method as recited in claim 20 further comprising the step of
coupling a running/pulling tool to an end of said valve body distal to
said process fluid outlet, said valve removably locatable in a mandrel
within a subterranean well.
38. The method as recited in claim 20 wherein said valve is located in a
side pocket mandrel associated with production tubing in a subterranean
well, said method further comprising the steps of:
receiving a process fluid into a casing surrounding said production tubing;
and
transferring said process fluid to within said production tubing at said
rate of process fluid flow via said valve.
39. A remotely-adjustable valve employable in an enhanced-lift recovery
system, comprising:
an elongated valve body having a process fluid inlet and a process fluid
outlet;
an elongated valve stem disposed within said valve body for axial
displacement relative thereto to adjust a rate of process fluid flow
between said fluid inlet and said fluid outlet as a function of a relative
axial position of said valve stem with respect to said valve body, said
valve body and said valve stem defining a compensation pressure chamber at
an end distal to said process fluid outlet, said valve stem including a
compensation pressure port allowing fluid communication between said
compensation pressure chamber and an environment surrounding said process
fluid inlet;
a cam disposed within said valve body and coupling said valve body and said
valve stem, said cam providing a plurality of axial displacement positions
thereon to place said valve stem at a selected one of a plurality of
relative axial positions with respect to said valve body, said valve body
having a control fluid pressure port for allowing a control fluid pressure
to be introduced into and released from said valve to reciprocate said
valve stem axially with respect to said valve body between cocked and set
positions, said cam moving from a first axial displacement position to a
second axial displacement position as said valve stem is reciprocated, a
difference between said first and second axial displacement positions
thereby causing an adjustment of said rate of process fluid flow between
said fluid inlet and said fluid outlet.
40. The valve as recited in claim 39 wherein said cam is rotatable and
provided with a J-slot about a circumference thereof, said J-slot adapted
to receive a follower therein to govern said relative axial position of
said valve stem with respect to said valve body, said J-slot having a
plurality of intermediate passages coupling said plurality of axial
displacement positions.
41. The valve as recited in claim 39 further comprising a follower coupling
said valve body to said cam.
42. The valve as recited in claim 39 wherein said valve stem comprises a
differential piston, said differential piston being reciprocable within a
chamber of said valve body and defining a control fluid chamber about said
differential piston, introduction of said control fluid pressure into said
control fluid chamber causing said valve stem to move into a cocked
position.
43. The valve as recited in claim 39 wherein said plurality of axial
displacement positions are aperiodically distributed.
44. The valve as recited in claim 39 further comprising a sensor for
relaying data concerning said valve to a remote location, said sensor
selected from the group consisting of:
a tubing pressure transducer, and
a valve stem axial displacement transducer.
45. The valve as recited in claim 39 wherein said cam provides more than
one axial displacement positions thereon.
46. The valve as recited in claim 39 wherein said cam provides an axial
displacement position in which said valve stem closes said valve.
47. The valve as recited in claim 39 wherein said valve body is operable to
be disposed within a side pocket mandrel associated with a well flow
conductor.
48. The valve as recited in claim 39 further comprising a spring biasing
said valve stem toward a closed position with respect to said valve body.
49. The valve as recited in claim 39 further comprising a remote source of
controllable hydraulic pressure coupled to said control fluid pressure
port, said remote source capable of establishing and interrupting a
prescribed pressure to reciprocate said valve stem within said valve body.
50. The valve as recited in claim 39 wherein a process fluid is a gas.
51. The valve as recited in claim 39 wherein said process fluid inlet
communicates with a casing of a subterranean well.
52. The valve as recited in claim 39 wherein said process fluid outlet
communicates with production tubing located within a casing of a
subterranean well.
53. The valve as recited in claim 39 further comprising a check valve to
prevent substantial process fluid flow from said process fluid outlet to
said process fluid inlet.
54. The valve as recited in claim 39 wherein said control fluid pressure is
produced by a control fluid selected from the group consisting of
hydraulic fluid and gas.
55. The valve as recited in claim 39 wherein first and second annular seals
disposed about said valve body cooperate with a mandrel surrounding said
valve body to create an annular chamber to receive a control fluid for
introduction into said valve via said control fluid pressure port.
56. The valve as recited in claim 39 further comprising a running/pulling
tool coupled to an end of said valve body distal to said process fluid
outlet, said valve removably locatable in a mandrel within a subterranean
well.
57. The valve as recited in claim 39 wherein said valve is located in a
side pocket mandrel associated with production tubing in a subterranean
well, a casing surrounding said production tubing adapted to receive a
process fluid and transfer said process fluid to within said production
tubing at said rate of process fluid flow via said valve.
58. A method of remotely adjusting a valve employable in an enhanced-lift
recovery system, comprising the steps of:
introducing a control fluid pressure into a control fluid pressure port in
an elongated valve body, said valve body having a process fluid inlet and
a process fluid outlet;
axially displacing an elongated valve stem disposed within said valve body
from a first set position to a cocked position, said valve stem axially
displaceable relative to said valve body to adjust a rate of process fluid
flow between said fluid inlet and said fluid outlet as a function of a
relative axial position of said valve stem with respect to said valve
body, said valve body and said valve stem defining a compensation pressure
chamber at an end distal to said process fluid outlet, said valve stem
including a compensation pressure port allowing fluid communication
between said compensation pressure chamber and an environment surrounding
said process fluid inlet;
moving a cam from a first axial displacement position to an intermediate
position with said valve stem, said cam disposed within said valve body
and coupling said valve body and said valve stem, said cam providing a
plurality of axial displacement positions thereon to place said valve stem
at a selected one of a plurality of relative axial positions with respect
to said valve body; and
releasing said control fluid pressure, said valve stem moving said cam from
said intermediate position to a second axial displacement position, a
difference in said first and second axial displacement positions thereby
causing an adjustment of said rate of process fluid flow between said
fluid inlet and said fluid outlet.
59. The method as recited in claim 58 wherein said step of moving comprises
the step of rotating said cam, said cam provided with a J-slot about a
circumference thereof, said J-slot adapted to receive a follower therein
to govern said relative axial position of said valve stem with respect to
said valve body, said J-slot having a plurality of intermediate passages
coupling said plurality of axial displacement positions.
60. The method as recited in claim 58 wherein said step of moving comprises
the step of sliding, with respect to said cam, a follower coupling said
valve stem to said cam.
61. The method as recited in claim 58 wherein said valve stem comprises a
differential piston, said differential piston being reciprocable within a
chamber of said valve body and defining a control fluid chamber about said
differential piston, said step of axially displacing comprising the step
of introducing of said control fluid pressure into said control fluid
chamber, thereby causing said valve stem to move into a cocked position.
62. The method as recited in claim 58 wherein said plurality of axial
displacement positions are aperiodically distributed.
63. The method as recited in claim 58 further comprising the step of
relaying data concerning said valve from a sensor to a remote location,
said sensor selected from the group consisting of:
a tubing pressure transducer, and
a valve stem axial displacement transducer.
64. The method as recited in claim 58 wherein said cam provides at least
three axial displacement positions thereon.
65. The method as recited in claim 58 wherein said cam provides an axial
displacement position in which said valve stem closes said valve, said
method further comprising the step of closing said valve with said valve
stem.
66. The method as recited in claim 58 further comprising the step of
disposing said valve within a side pocket mandrel associated with a well
flow conductor.
67. The method as recited in claim 58 further comprising the step of
biasing said valve stem toward a closed position with respect to said
valve body with a spring.
68. The method as recited in claim 58 further comprising the step of
establishing and interrupting a prescribed pressure to reciprocate said
valve stem within said valve body with a remote source of controllable
hydraulic pressure coupled to said control fluid pressure port.
69. The method as recited in claim 58 further comprising the step of
relaying data concerning said valve from a sensor to a remote location,
said sensor selected from the group consisting of:
a tubing pressure transducer, and
a valve stem axial displacement transducer.
70. The method as recited in claim 58 further comprising the step of
communicating fluid between said process fluid inlet and a casing of a
subterranean well.
71. The method as recited in claim 58 further comprising the step of
communicating fluid between said process fluid outlet and production
tubing located within a casing of a subterranean well.
72. The method as recited in claim 58 further comprising the step of
preventing substantial process fluid flow from said process fluid outlet
to said process fluid inlet with a check valve.
73. The valve as recited in claim 58 wherein said control fluid pressure is
produced by a control fluid selected from the group consisting of
hydraulic fluid and gas.
74. The method as recited in claim 58 wherein first and second annular
seals disposed about said valve body cooperate with a mandrel surrounding
said valve body to create an annular chamber, said method further
comprising the step of receiving a control fluid into said annular chamber
for introduction into said valve via said control fluid pressure port.
75. The method as recited in claim 58 further comprising the step of
coupling a running/pulling tool to an end of said valve body distal to
said process fluid outlet, said valve removably locatable in a mandrel
within a subterranean well.
76. The method as recited in claim 58 wherein said valve is located in a
side pocket mandrel associated with production tubing in a subterranean
well, said method further comprising the steps of:
receiving a process fluid into a casing surrounding said production tubing;
and
transferring said process fluid to within said production tubing at said
rate of process fluid flow via said valve.
77. A remotely-adjustable valve employable in an enhanced-lift recovery
system, comprising:
an elongated valve body having a process fluid inlet and a process fluid
outlet;
an elongated valve stem disposed within said valve body for axial
displacement relative thereto to adjust a rate of process fluid flow
between said fluid inlet and said fluid outlet as a function of a relative
axial position of said valve stem with respect to said valve body;
a cam follower disposed within said valve body and coupling said valve body
and said valve stem, said cam follower following a prescribed path defined
by a camming surface within said valve body to translate a reciprocating
axial movement of said valve stem to set said valve stem at a
predetermined axial displacement, said valve body having a control fluid
pressure port for allowing a control fluid pressure to be introduced into
and released from said valve to reciprocate said valve stem axially with
respect to said valve body between cocked and set positions, said cam
follower following said camming surface from a first axial displacement
position to a second axial displacement position as said valve stem is
reciprocated, a difference between said first and second axial
displacement positions thereby causing an adjustment of said rate of
process fluid flow between said fluid inlet and said fluid outlet.
78. The valve as recited in claim 77 wherein said valve stem comprises a
differential piston, said differential piston being reciprocable within a
chamber of said valve body and defining a control fluid chamber about said
differential piston, introduction of said control fluid pressure into said
control fluid chamber causing said valve stem to move into a cocked
position.
79. The valve as recited in claim 77 wherein said valve body and said valve
stem define a compensation pressure chamber at an end distal to said
process fluid outlet, said valve body including a compensation pressure
port allowing fluid communication between said compensation pressure
chamber and an environment surrounding said distal end.
80. The valve as recited in claim 77 wherein said valve body and said valve
stem define a compensation pressure chamber at an end distal to said
process fluid outlet, said valve stem including a compensation pressure
port allowing fluid communication between said compensation pressure
chamber and an environment surrounding said process fluid inlet.
81. The valve as recited in claim 77 further comprising a remote source of
controllable hydraulic pressure coupled to said control fluid pressure
port, said remote source capable of establishing and interrupting a
prescribed pressure to reciprocate said valve stem within said valve body.
82. The valve as recited in claim 77 further comprising a sensor for
relaying data concerning said valve to a remote location, said sensor
selected from the group consisting of:
a tubing pressure transducer, and
a valve stem axial displacement transducer.
83. The valve as recited in claim 77 further comprising a check valve to
prevent substantial process fluid flow from said process fluid outlet to
said process fluid inlet.
84. The valve as recited in claim 77 wherein said control fluid pressure is
produced by a control fluid selected from the group consisting of
hydraulic fluid and gas.
Description
TECHNICAL FIELD OF THE INVENTION
The present invention is directed, in general, to a choke valve, and more
specifically, is directed to a remotely actuated adjustable downhole choke
valve that may be used in the production and operation of a well.
BACKGROUND OF THE INVENTION
In producing liquids, including oil and water, from a geological formation,
most wells initially have sufficient natural bottom hole pressure to
efficiently lift the liquids up to the ground surface. However, over a
period of time, this natural bottom hole pressure declines, thus requiring
artificial steps to improve lift. One commonly known method of augmenting
lift is to inject gas into the production tubing. This injection is
usually done by forcing gas down the annulus between the production
tubing, which conducts liquid to the surface, and the casing of the well.
The gas is constrained to flow through a gas flow control device at the
desired depth into the production tubing. The gas bubbles mix with the
liquids and reduce the overall density of the mixture. With the liquid's
density reduced, the diminished natural bottom hole pressure is then able
to lift the liquid to the surface. This injection of gas into the well
requires the operation of a gas lift control valve that regulates the
injection of gas flow into the tubing.
In conventional applications, various types of lifting gas injection
control valves can be utilized. Among the simplest of these is the orifice
valve, which consists of a specifically-sized orifice insert mounted in
the valve body and a back-flow check. The size of the orifice used is
normally chosen based on calculated or estimated parameters, and therefore
may or may not prove to be optimal in the actual application. Furthermore,
in order to confirm whether or not the chosen orifice size is optimal, it
may be necessary to remove and replace the valve one or more times using
different orifice sizes to compare well performance data. Each act of
removing and replacing the valve requires an interruption of well
production as well as a period of time for the well to re-stabilize before
useful comparative production data can be obtained. Additionally, an
artificial-lift well whose reservoir characteristics are of a transient
nature may require regular changing of the lifting valve orifice in order
to maintain optimal conditions. A significant disadvantage with this
system is that several trips into and out of the hole have to be conducted
to achieve the proper setting. These multiple trips are, of course, time
consuming and costly.
The operating valve of an artificial lift installation is normally intended
to regulate or restrict the flow of injection gas from the casing into the
production tubing and allow the flow of injected in response to either a
preselected pressure condition or control from the surface. A difficulty
inherent in the use of gas lift valves which are either fully open or
closed is that gas lift production completions are closed fluid systems
which are highly elastic in nature due to the compressibility of the
fluids and the frequently large depth of the wells. For this reason, and
especially in the case of dual completion wells, the flow of injected gas
through a full open gas lift valve may produce vibrations at a harmonic
frequency of the closed system and thereby create resonant oscillations in
the system generating extremely large and destructive forces within the
production equipment. Gas lift valves of a particular size aperture
positioned at a point of resonance within the well completions(s) may have
to be replaced in order for the system to be operable.
Another application of downhole fluid control valves within a production
well is that of chemical injection. In some wells, it becomes necessary to
inject a flow of chemicals into the borehole in order to treat either the
well production equipment or the formation surrounding the borehole. The
introduction of chemicals through a downhole valve capable of only fully
open or fully closed positions does not allow precise control over the
quantity of chemicals injected into the well.
Another application of downhole flow control valves is that of a dual
completion gas lift operation in a well. By varying the orifice size of
the gas injection valve the differential pressure drop across the gas lift
valve can be controlled so that the pressure of the gas inside each string
of tubing at the injection valve can be matched with the needs of that
particular formation. However, flow control valves capable of only fully
open or closed configurations contribute to imprecise control over the
pressure drop. In addition, such systems also suffer from potential
resonance due to oscillations generated by flow through the valve which
may necessitate tuning the system in some fashion or replacement of the
valve in order for the system to be operable.
Yet another application of downhole fluid control valves is in "auto
lifting" applications. Auto lifting occurs where gas from one geological
formation at a relatively higher pressure is used to supply the lifting
energy to the liquids from a separate formation, all within the same
wellbore.
As mentioned above, prior art flow control valves for downhole
applications, such as gas lift valves, include a number of inherent
disadvantages. A first disadvantage is having a single size flow orifice
in the open condition which may produce resonant oscillations resulting in
destructive effects within the well. A second disadvantage is that of
being capable of assuming only a fully open or fully closed position which
requires the shuttling of the valve between these two positions at high
pressures and results in tremendous wear and tear on the valves. Such wear
requires frequent maintenance or replacement of the valves which is
extremely expensive.
Another type of valve utilized in gas lift applications is a hydraulic
actuated valve that is generally controlled from the surface. By
controlling the flow of a hydraulic fluid from the surface, a poppet valve
is actuated to control the flow of fluid into the gas lift valve. The
valve is moved from a closed position to an open position for as long as
necessary to effect the flow of the lift gas. Such valves are also
position instable, that is upon interruption of the hydraulic control
pressure, the gas lift valve returns to its normally closed configuration.
Other hydraulically actuated downhole flow control valves also include
certain inherent disadvantages as a result of their long hydraulic control
lines which result in a delay in the application of control signals to a
downhole device. For example, in applications involving hydraulically
driven motors or pistons, the precise flow of hydraulic fluid necessary to
adjust the valve to essential critical tolerances is often difficult to
achieve due to the hysteresis that develops in a hydraulic system that
spans substantial well depths. Another complicating factor is the
hydraulic head that is present at those same well depths. At such depths,
the pressure attributable to the head of hydraulic fluid can become quite
significant, which makes the setting of the valve more difficult because
of the added hydraulic pressure that must be compensated for when
adjusting the valve. These problems exist primarily because the point of
fine tuning for the valve depends on the flow of hydraulic fluid that is
controlled from the distant surface, and for the reasons stated above,
fine tuning adjustment to the valve is difficult to achieve.
To overcome some of the above-described disadvantages, electrically
controlled gas lift valves have been developed. However, some of these
valves, such as the one disclosed in U.S. Pat. No. 3,427,989, also suffer
from disadvantages of position instability and operation based upon either
fully open or fully closed conditions. Another electrical valve, which is
disclosed in pending U.S. application, Ser. No. 08/218,375 and is
incorporated herein by reference, addresses many of the problems suffered
by prior electrical control valves by providing an electrical valve that
allows the adjustment of a variable orifice size valve by means of signals
from the surface. While these valves are well suited for their intended
use, they are more expensive and complex in their design than the
conventional hydraulic valves discussed above.
Thus, it is apparent that there is a need in the art for an inexpensive,
simply designed, fluid actuated control valve in which the orifice size of
the valve is adjustable through a range of values that would enable gas
lift systems, which are susceptible to resonant oscillation, to be detuned
by adjusting the size of the orifice to dissipate the resonant
oscillations. Such a variable orifice valve would allow much greater
control over the quantity and rate of injection of fluids into the well.
In particular, more precise control over the flow of injection gas into a
dual lift gas lift well completion would allow continuous control of the
injection pressure in both strings of tubing from a common annulus, which
would result in more efficient production from the well.
There is also a need in the art for a fluid actuated control valve that
would be position stable; that is, it would be able to set a flow control
valve at a particular orifice size and to have it remain at that same
orifice size until selectively changed to a different size without the
need for well intervention to change the orifice size, i.e., pulling the
valve. There is also a need in the art for a fluid actuated control valve
that is able to monitor not only the orifice size of the valve but also
the pressures and flow rates within the production system in order to
obtain desired production parameters within the well.
The fluid actuated flow control valve system of the present invention
provides a valve system that addresses the deficiencies of the prior art
valves.
SUMMARY OF THE INVENTION
To address the above-discussed deficiencies of the prior art, it is a
primary object of the present invention to provide a remotely-adjustable
hydraulically-actuated valve that overcomes both the sensitivity of prior
art remotely-adjustable hydraulically-actuated valves to inevitable
variations in hydraulic pressure and response times and the sheer
complexity and cost of prior art remotely-adjustable electrically-actuated
valves.
In the attainment of the above-described primary object, the present
invention provides a remotely-adjustable valve employable in an
enhanced-lift recovery system and a method of adjusting the same. The
valve comprises: (1) an elongated valve body having a process fluid inlet
and a process fluid outlet, (2) an elongated valve stem disposed within
the valve body for axial displacement relative thereto to adjust a rate of
process fluid flow between the fluid inlet and the fluid outlet as a
function of a relative axial position of the valve stem with respect to
the valve body and (3) a cam disposed within the valve body and coupling
the valve body and the valve stem, the cam providing a plurality of axial
displacement positions thereon to place the valve stem at a selected one
of a plurality of relative axial positions with respect to the valve body,
the valve body having a control fluid pressure port for allowing a control
fluid pressure to be introduced into and released from the valve to
reciprocate the valve stem axially with respect to the valve body between
cocked and set positions, the cam moving from a first axial displacement
position to a second axial displacement position as the valve stem is
reciprocated, a difference between the first and second axial displacement
positions thereby causing an adjustment of the rate of process fluid flow
between the fluid inlet and the fluid outlet.
As mentioned above, prior art flow control valves for downhole
applications, such as gas lift valves, include a number of inherent
disadvantages. A first of these is having a single size orifice in the
open condition that may produce resonant oscillations resulting in
destructive effects within the well. The single size orifice of these
prior art valves further requires a lengthy and expensive trial and error
process of running a valve having a fixed orifice of a given size,
allowing the well to reach a steady state, determining production rate and
repeating the first three steps to determine production rate as a function
of the orifice size to optimize production from the well.
A second disadvantage of some prior art hydraulically-actuated valves is
that of being capable of assuming only a full open or full closed
position, requiring that shuttling of the valve between these two
positions at high pressures and results in significant wear on the valves.
Such wear requires frequent maintenance or replacement of the valves,
which is expensive. Prior art hydraulically-actuated downhole flow control
valves also include certain inherent disadvantages as a result of their
long hydraulic control lines, resulting in a hysteresis in the application
of control signals to the downhole valve. In addition, the prior art
valves did not accommodate telemetry circuitry to relay information from
the valve to controls at the surface.
The present invention overcomes the disadvantages of these prior art
hydraulically-actuated valves by providing a hydraulically-actuated valve
having an orifice that is adjustable through a range of discrete sizes.
This enables systems, such as gas lift systems which are susceptible to
resonant oscillation, to be detuned by adjusting the size of the orifice
so that the system is no longer resonant. In addition, an adjustable
orifice allows control over the quantity and rate of injection of fluids
into the well. In particular, more precise control over the flow of
injection gas into a dual lift gas lift well completion would allow
continuous control of the injection pressure in both strings of tubing
from a common annulus. This permits controls of production pressures and
flow rates within the wells and results in more efficient production from
the well.
In stark contrast to the conventional hydraulically-actuated valves, the
present invention employs a novel cam arrangement that removes any
sensitivity of the valve to the variations or delays in hydraulic pressure
that plagued those valves. The cam translates a simple on-off application
of hydraulic pressure into valve stem reciprocation and a transition
between predetermined discrete valve positions. Thus, variations or delays
that would have resulted in erroneous flow rates in the prior art valves
instead are of no effect whatsoever.
In the past, it was felt that only electrically-actuated valves possessed
the requisite controllability to overcome the disadvantages of
hydraulically-actuated valves. However, the present invention demonstrates
that predictable hydraulic control is an excellent alternative to the
electrically-actuated valves disclosed in the prior art.
Another desirable characteristic of a downhole flow control valve system is
that of position stability of the flow control orifice. That is, it would
be highly useful to be able to set a flow control valve at a particular
orifice size and to have it remain the same until selectively changed to a
different size. Position stability is preferable in the absence of any
control signals to the valve so that applied power is only necessary to
change the orifice from one size to another. The valve of the present
invention employs defined axial displacement positions on the cam to
ensure that the valve stem remains at its position in the absence of
hydraulic pressure. Pressure is applied only to transition the valve to
another size.
In a preferred embodiment of the present invention, the cam is rotatable
and provided with a J-slot about a circumference thereof, the J-slot
adapted to receive a follower therein to govern the relative axial
position of the valve stem with respect to the valve body, the J-slot
having a plurality of intermediate passages coupling the plurality of
axial displacement positions. As will be described, the J-slot cooperates
with a follower to place the follower in a selected axial position when
the follower is shifted axially with respect to the J-slot. The present
invention makes notably advantageous use of the J-slot concept to provide
predictable control of a valve.
In a preferred embodiment of the present invention, the valve further
comprises a follower coupling the valve body to the cam. Thus, the
follower traverses the J-slot when the valve stem is reciprocated with
respect to the valve body. In such an arrangement, the cam is axially
fixed with respect to the valve stem, although it is free to rotate. In
the alternative, the cam may be axially fixed with respect to the valve
body and the follower may be mounted to the valve stem. In either
arrangement, the result is the same.
In a preferred embodiment of the present invention, the valve stem
comprises a differential piston that is reciprocable within a sleeve of
the valve body and defining a control fluid chamber about the differential
piston; introduction of the control fluid pressure into the control fluid
chamber causes the valve stem to move into a cocked position. A
differential piston is defined as a duality of spaced-apart pistons having
different surface areas that are coupled to one another to move in the
same direction. When pressure is applied to the space between the pistons,
the pressure applies a larger force to the piston of larger surface area
than to the piston of smaller surface area, causing both pistons to move
in the direction of the force acting on the piston having the larger
surface area. The present invention employs a differential piston to allow
control fluid pressure to build to a significant level before effecting
piston movement, thereby decreasing sensitivity of the valve to pressure
anomalies or delays.
In a preferred embodiment of the present invention, the valve body and the
valve stem define a compensation pressure chamber at an end distal to the
process fluid outlet, the valve body including a compensation pressure
port allowing fluid communication between the compensation pressure
chamber and an environment surrounding the distal end. The environment
surrounding the distal (usually the upper) end is typically the production
tubing. Therefore, tubing pressure may be brought to bear against the
valve stem. This tubing pressure counteracts process fluid inlet pressure
(typically casing pressure) brought to bear in the opposite direction.
In a preferred embodiment of the present invention, the valve body and the
valve stem define a compensation pressure chamber at an end distal to the
process fluid outlet, the valve stem including a compensation pressure
port allowing fluid communication between the compensation pressure
chamber and an environment surrounding the process fluid inlet. In
applications in which casing pressure is significantly greater than tubing
pressure, the previously-described pressure compensation scheme may be
inadequate to prevent the valve stem from floating in the valve body and
therefore changing the orifice size. In such applications, the process
fluid inlet pressure may be introduced into the compensation pressure
chamber via the compensation pressure port to minimize any sensitivity
tubing pressures. Another benefit associated with this modification is
that the upper chamber is exposed to the relatively cleaner injection gas
environment of the casing rather than the often polluted production fluid
environment of the tubing. Therefore, the interior of the valve is exposed
to a relatively cleaner and contaminate free environment. In some
instances, the fluid within the tubing may have components such as
geological sedimentation, water and other substances such as corrosive
minerals mixed in with the fluid, which may prevent the valve from
functioning properly. The injection gas is, of course, free from these
pollutants, which are not present to interfere with the valve's operation.
In a preferred embodiment of the present invention, the cam provides more
than one displacement positions thereon. Thus, in the embodiment
illustrated, the cam provides more positions, the maximum number of which
is limited by the physical geometry and overall design of the valve,
particularly the circumference of the cam and the width of the passages of
the J-slot.
In a preferred embodiment of the present invention, the cam provides an
axial displacement position in which the valve stem closes the valve. As
will be described, the closed position is most useful for diagnostic
purposes. In valves not provided with displacement sensors, provision of
the closed position allows surface determination of the valve state. This
is valuable if the position of the valve cannot be readily determined or
has been forgotten.
In a preferred embodiment of the present invention, the valve body is
operable to be disposed within a side pocket mandrel associated with a
well flow conductor. Those of ordinary skill in the art are similarly
familiar with the use of a side pocket mandrel to house a gas lift valve.
The valve of the present invention is substantially the same length, the
same diameter, and has the same center of gravity and mass as prior art
valves. This is important in providing a wire line retrievable gas lift
valve that can be used in deviated wells having a maximum deviation of
approximately 70 degrees.
In a preferred embodiment of the present invention, the valve further
comprises a spring biasing the valve stem toward a closed position with
respect to the valve body. The spring counteracts any tendency of the
valve stem to float, thereby increasing orifice size. Application of
hydraulic pressure from the surface counteracts the force of the spring,
allowing the valve stem to reciprocate and set at a different axial
position and orifice size.
In a preferred embodiment of the present invention, the valve further
comprises a remote source of controllable hydraulic pressure coupled to
the control fluid pressure port, the remote source capable of establishing
and interrupting a prescribed pressure to reciprocate the valve stem
within the valve body. As previously described, the present invention
merely requires an intermittent source of hydraulic pressure exceeding a
threshold minimum pressure. The actual pressure and the rate at which the
pressure is applied are not material to operation of the valve, as long as
the pressure is sufficient to reciprocate the valve stem.
In a preferred embodiment of the present invention, the valve further
comprises a sensor for relaying data concerning the valve to a remote
location, the sensor selected from the group consisting of: (1) a tubing
pressure transducer and (2) a valve stem axial displacement transducer.
Another significant advantage that is highly desirable in downhole flow
control valve systems is that of an accurate system for monitoring not
only the orifice size of the valve but the pressure of the production
tubing to obtain desired production parameters within the well. For
example, it is advantageous to select a particular bottom hole pressure
and then control the size of the orifice of the valve to obtain that
selected value of bottom hole pressure. Such systems require a reliable
means for both sending data uphole from the vicinity of the valve as well
as processing that data and then actively controlling the size of the flow
control orifice of the valve to obtain the desired results, as monitored
by the system.
In this preferred embodiment, the valve provides transducers for sensing
the displacement of the valve stem (and hence orifice size) and the tubing
pressure. Of course, other sensors, such as a flow rate transducer, are
within the broad scope of the present invention.
In a preferred embodiment of the present invention, the process fluid inlet
communicates with a casing of a subterranean well. Thus, casing pressure
preferably forces a process fluid in the casing through the valve of the
present invention. In gas lift systems wherein gas is forced through
tubing central to the casing to allow production through the casing, the
process fluid inlet would communicate instead with the tubing.
In a preferred embodiment of the present invention, the process fluid
outlet communicates with production tubing located within a casing of a
subterranean well. Thus, the process fluid preferably proceeds from the
valve into the production tubing through the valve of the present
invention. In gas lift systems wherein gas is forced through tubing
central to the casing to allow production through the casing, the process
fluid outlet would communicate instead with the casing.
In a preferred embodiment of the present invention, the valve further
comprises a check valve to prevent substantial process fluid flow from the
process fluid outlet to the process fluid inlet. The check valve disallows
backflow through the valve.
In a preferred embodiment of the present invention, first and second
annular seals disposed about the valve body cooperate with a mandrel
surrounding the valve body to create an annular chamber to receive a
control fluid for introduction into the valve via the control fluid
pressure port. As previously described, the valve of the present invention
preferably resides within a side pocket mandrel. Rather than running a
hydraulic hose with the valve, the valve may preferably be lowered into a
mandrel having an integral hydraulic pressure port. The valve is sealingly
engaged with the pressure port, allowing fluid pressure developed in the
port to reciprocate the valve stem.
In a preferred embodiment of the present invention, the valve further
comprises a running/pulling tool coupled to an end of the valve body
distal to the process fluid outlet, the valve removably locatable in a
mandrel within a subterranean well. The running/pulling tool allows the
valve to be set in place and retrieved if desired. Often, it is
advantageous to replace the valve of the present invention with a valve
having a fixed orifice size once the valve of the present invention is
used to determine the optimum orifice size.
In a preferred embodiment of the present invention, the valve is located in
a side pocket mandrel associated with production tubing in a subterranean
well, a casing surrounding the production tubing adapted to receive a
process fluid and transfer the process fluid to within the production
tubing at tile rate of process fluid flow via the valve. As those of
ordinary skill in the art recognize, this represents an advantageous
environment for operation of the valve of the present invention.
In a preferred embodiment of the present invention, the process fluid is a
gas. Those of ordinary skill in the art will understand that the valve of
the present invention may also meter the flow of liquids from the casing
into the production tubing.
The foregoing has outlined rather broadly the features and technical
advantages of the present invention so that those skilled in the art may
better understand the detailed description of the invention that follows.
Additional features and advantages of the invention will be described
hereinafter that form the subject of the claims of the invention. Those
skilled in the art should appreciate that they may readily use the
conception and the specific embodiment disclosed as a basis for modifying
or designing other structures for carrying out the same purposes of the
present invention. Those skilled in the art should also realize that such
equivalent constructions do not depart from the spirit and scope of the
invention in its broadest form.
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present invention, and the
advantages thereof, reference is now made to the following descriptions
taken in conjunction with the accompanying drawings, in which:
FIG. 1 illustrates a schematic side cross-sectional view of a prior art gas
lift system;
FIG. 2 illustrates a schematic cross-sectional view of the fluid actuated
control valve, shown in phantom, positioned within a side-pocket mandrel
in relation to the casing and tubing;
FIG. 3 illustrates a partial cut-away, cross-sectional view of an overall
view of the valve;
FIG. 3A illustrates a partial cut-away, cross-sectional view of one
embodiment of the valve's upper portion having openings to the tubing;
FIG. 3B illustrates a partial cut-away, cross-sectional view of the upper
intermediate section of the valve illustrated in FIG. 3A;
FIG. 3C illustrates a partial cut-away, cross-sectional view of the lower
intermediate section of the valve illustrated in FIG. 3A;
FIG. 3D illustrates a partial cut-away, cross-sectional view of the lower
end section of the valve illustrated in FIG. 3A;
FIG. 3E illustrates a partial cut-away, cross-sectional view of another
embodiment of the valve's upper portion having the opening to the tubing
blocked and a passageway through the valve stem;
FIG. 3F illustrates a partial cut-away, cross-sectional view of the upper
intermediate section of the valve illustrated in FIG. 3E;
FIG. 3G illustrates a partial cut-away, cross-sectional view of the lower
intermediate section of the valve illustrated in FIG. 3E;
FIG. 3H illustrates a partial cut-away, cross-sectional view of the lower
end section of the valve illustrated in FIG. 3E;
FIG. 4A illustrates a schematic cross-sectional view of the valve
illustrated in FIGS. 3A-3D in the closed position;
FIG. 4B illustrates a schematic cross-sectional view of the valve
illustrated in FIGS. 3A-3D in the fully cocked position;
FIG. 4C illustrates a schematic cross-sectional view of the valve
illustrated in FIGS. 3A-3D in a representative, partially open,
operational position;
FIG. 4D illustrates a schematic cross-sectional view of the valve
illustrated in FIGS. 3E-3H having the passageway formed through a portion
of the valve stem;
FIG. 4E illustrates a schematic cross-sectional view of the valve
illustrated in FIG. 4D having a tubing pressure transducer, and a valve
stem axial displacement transducer;
FIG. 5 illustrates the valve's cam portion having a J-slot about its
circumference for providing a plurality of axial displacement positions
for the valve stem; and
FIG. 6 illustrates a laid-out plan view of the cam illustrated in FIG. 5
showing the plurality of intermediate passages with a follower pin
positioned therein for providing the plurality of axial displacement
positions for the valve stem.
DETAILED DESCRIPTION
Turning initially to FIG. 1 there is illustrated a schematic
cross-sectional view of a conventional gas lift configuration used in the
production of an oil well. Generally, when a reservoir is first produced,
there is sufficient natural pressure within the reservoir to push the
liquids to the surface and efficiently produce the well. However, after a
period of time, the natural formation pressure is abated, and while there
is still natural pressure within the reservoir, it is no longer adequate
to lift the liquids to the surface. In such instances, a gas lift system
is often employed. Gas 10, represented by the arrows, is injected into the
annulus 12 between the well casing 14 and the production tubing 16. The
gas 10 mixes with and reduces the density of the liquids, which allows the
remaining natural pressure to push the less dense liquids to the surface
and, thereby, commercially produce the well. It should be understood that
the configuration illustrated in FIG. 1 is an open end tubing
configuration and is representative in nature only and that various
conventional gas lift configurations and apparatus are well known. For
example, various types of gas lift valves that control the flow of gas
from the casing to the tubing are typically employed and are positioned
within a conventional mandrel pocket (not shown). The casing and tubing
are placed in fluid communication with one another via the gas lift valve
when the valve is in an open position.
Turning now to FIG. 2, there is illustrated a schematic view of the
elongated valve assembly of the present invention. In this figure, the
production tubing 18 is positioned within the casing 20 and centralized
with conventional packers 22. The valve assembly 24, shown in phantom, is
positioned within a mandrel pocket 26 in the interior of the mandrel 28.
Though the mandrel 28 may have various configurations, it is preferred
that the mandrel 28 is a threaded collar member that can be threadedly
attached to the production tubing 18. The mandrel pocket 26 is located
within the interior of the mandrel 28 and is configured to securely hold
the valve assembly 24 in a manner hereinafter described. Connected to the
exterior of the mandrel 28 and in fluid communication with the valve
assembly 24 is a fluid control line 30 that extends to the surface. The
fluid control line 30 serves as a conduit through which the control fluid
flows to actuate the valve assembly 24. As used herein, the term control
fluid is intended to include liquids, such as hydraulic fluids, gas, and
similar type fluids. By conventional means, the fluid flow may be
controlled from the surface to remotely adjust and actuate the valve
assembly 24.
The control line 30 may also include a "T" on a manifold connected to a
container (not shown) at the surface with a velocity check (not shown)
also on the control line 30. The "T", container and velocity check can aid
in controlling pressure increases in the control line 30 that are the
result of increases in temperature of the control fluid within the control
line 30. Thus, as the pressure of the control fluid increases, the control
line fluid can be released into the container at the "T" on the manifold.
Even without such a "T" on the manifold, or other similar mechanism to
relieve buildup of pressure, the valve assembly 24 of the present
invention handles a limited change in pressure in the control line 30
because the valve will not move to an open position until the spring force
is overcome by the pressure from the control line 30.
Hydraulic-pressure actuation of the valve assembly 24 is certainly viable,
and may have some advantages over gas. However, in certain applications,
using gas as the control fluid, in place of hydraulic fluids, has certain
advantages. One such advantage is that using gas minimizes static fluid
head in the control line, which, in turn, allows the use of a lighter
spring within the valve. Due to the presence of the hydraulic fluid in the
control line between the valve and the surface, the hydrostatic head has
the effect of limiting certain performance parameters. For example,
because of the presence of the hydrostatic head a heavier spring must be
used in the valve. It follows that if the control line static pressure
head can be minimized, the performance envelope of the valve can be
expanded (performance envelope meaning the range of conditions in which
the device can be utilized). Additionally, there is practically no limit
to the depth at which a particular valve could be run, and the change in
pressure in the control line caused by an increase in temperature would
tend not to shift the valve if gas were used as a control line fluid,
since the gas would be more readily compressed. Another advantage of using
gas is that pressure activation response time (i.e., the time required for
the entire system to equalize after application of pressure at the
surface) would be much faster both for pressurization and bleed-off of the
control line, due to the viscosity differences in the medium.
Turning now to FIGS. 3 and 3A through 3D, there is illustrated a preferred
embodiment of the elongated valve assembly 24 of the present invention. To
show the detail necessary for a detailed discussion, the valve assembly 24
is illustrated in four views, 3A through 3D. Thus, it is understood that
FIGS. 3A-3D collectively illustrate the entire length of this particular
embodiment of the valve assembly 24 as shown in FIG. 3. Basically, the
valve assembly 24 is comprised of a latch assembly 32, an elongated valve
body 34, which includes a valve mechanism, and a conventional check valve
assembly 36. The valve body 34 has tubing fluid outlet ports 38, casing
fluid inlet ports 40 and a control fluid port 42. Spaced along the length
of the valve body 34 are a plurality of packing sections 44 that extend
around the circumference of the valve body 34.
Turning now to FIG. 3A for a more detailed discussion of the valve assembly
24, the conventional latch assembly 32 has a profile formed by first 46a,
second 46b and third 46c shoulders. The profile shoulders 46a, 46b and 46c
allow engagement of running and pulling tools that are used in setting the
valve assembly 24 in place within the pocket mandrel. The valve assembly
24 may be set and retrieved by conventional methods such as a wireline.
The latch assembly 32 is comprised of a central mandrel 48 received within
a latching sleeve 50, both of which extend to a lock collar assembly 52,
which is also a part of the latch assembly 32. The lock collar assembly 52
is comprised of a lock collar 54 and a threaded lock collar nipple 56. An
end portion 58 of the latching sleeve 50 is received between the lock
collar 54 and a portion of the lock collar nipple 56, which holds and
centralizes the lock collar 54 with respect to the valve assembly 24. The
lock collar 54 has an angled shoulder profile that engages a "crescent
shape" matching profile formed in an interior wall of the mandrel pocket.
When the valve assembly 24 is correctly positioned in the mandrel pocket,
the lock collar 54 engages the mandrel's matching profile and locks the
valve assembly 24 in the proper orientation and location with respect to
the mandrel pocket.
A shear pin 60 extends through the latching sleeve 50 and the central
mandrel 48. The shear pin 60 holds a spring 62 in a compressed position
and prevents the spring 62 from biasing the latching sleeve 50 in an
upward direction from the lock collar 54. If it is desired to remove the
valve assembly 24 from the mandrel pocket, sufficient pulling force is
exerted on the latching sleeve 50 to shear the shear pin 60. The latching
sleeve 50 then moves upward from between the lock collar 54 and the lock
collar nipple assembly 52, which allows the lock collar 54 to disengage
from the matching profile within the mandrel pocket. The valve assembly 24
may then be removed from the mandrel pocket.
Positioned immediately below the lock collar 54 is a roll pin 64 that
extends through the lock collar assembly 52 and into the central mandrel
48 to prevent rotation therebetween. A 45.degree. step change no-go
shoulder 66 is formed immediately under the lock collar 54 on the lock
collar nipple 56. The "no-go" shoulder 66 serves two functions. First, it
stops the downward motion of the valve assembly 24 as it is being inserted
into the mandrel pocket. Second, the 45.degree. profile matches a
corresponding shoulder profile at the entrance of the mandrel pocket to
properly locate the valve assembly 24 within the mandrel pocket. The
tubing inlet port 38, which opens to the tubing, is formed in the lock
collar assembly 54. The tubing inlet port 38 may allow process fluid from
the tubing to enter and exit the valve body 34. The elongated valve body
34 that comprises a portion of the elongated valve assembly 24 is
threadedly received in the end of the lock collar assembly 52 opposite
that in which the central mandrel 48 is threadedly received.
Turning now to FIG. 3B, disposed within the valve body 34 is an elongated
valve stem 68 that is axially displaceable within the valve body 34 and
extends a substantial portion of the length of the valve body 34. The
valve stem 68 is axially displaceable relative to the valve body 34 to
adjust a rate of process fluid flow between the tubing fluid outlet ports
38 and casing fluid inlet ports 40 (FIG. 3) as a function of the relative
axial position of the valve stem 68 with respect to the valve body 34.
The valve stem 68 is comprised of a differential piston assembly 70 from
which an elongated actuator mandrel 72 extends toward the check valve
assembly 36. The actuator mandrel's 72 diameter is such that it does not
fill the entire hollow interior volume of the valve body 34. As such, an
interior volume 74 is defined within the valve body 34 that allows the
casing fluid to flow into the interior of the valve body 34 via the casing
fluid inlet ports 40 and from the interior of the valve body 34 into the
interior of the tubing via the tubing outlet ports 38. This fluid flow, of
course, subjects the interior portions of the valve body 34 to the
pressures associated with such fluid flow; the ramifications of which is
discussed below. Preferably, the differential piston assembly 70 has a
first end portion 76, which is coupled to the valve stem 68 by cooperating
female threads 78 on the first end portion 76 and male threads 80 on the
end of the valve stem 68. The differential piston assembly 70 further
includes an opposing second end portion 82 that has a smaller diameter
area than the first end portion 76 and a reduced diameter portion 84
intermediate the first and second end portions 76,82 and that includes a
cam support shoulder 87.
A hollow cylinder portion or compensation pressure chamber 88 is formed in
the upper portion of the valve body 34 in which the differential piston
assembly 70 is reciprocable. More preferably, the upper end of the chamber
88 is configured to allow the larger first end portion 76 of the
differential piston assembly 70 to reciprocate within the upper end of the
chamber 88. However, in the preferred embodiment, a shoulder 89 exists at
the upper extremity of the chamber 88. When contacted by the upper surface
of the larger first end portion 76, the shoulder 89 prevents further axial
movement of valve stem assembly 68 in the upward direction.
A first seal 90, preferably an "O" ring, reinforced by an anti-extrusion
ring 92, extends around the circumference of the first end portion 76 of
the differential piston assembly 70 and a second seal 94, also preferably
an "O" ring, reinforced by an anti-extrusion ring 92, extends around the
second end portion 82. For reasons that will be discussed later, it is
significant to point out that the first seal 90 has a diameter larger than
that of the second seal 94. A control fluid chamber 96 is formed between
the first end 76 and second end 82 of the differential piston assembly 70
and is sealed by the first and second seals 90 and 94. Additionally, the
compensation pressure chamber 88 is formed between the upper wall of the
chamber 88 and the first end portion 76 of the differential piston
assembly 70 and is sealed from the control fluid chamber 96 by the first
seal 90. The control fluid port 42, which is formed through the valve body
34 adjacent the control fluid chamber 96, allows a control fluid to be
introduced into and released from the control fluid chamber 96 to
reciprocate the valve stem 68 axially with respect to the valve body 34.
Extending around the circumference of the valve body's 34 upper portion and
adjacent the chamber 88 is a first of three packing seals 44 comprising a
pair of opposing "v" ring nesting profiles 98 having an "O" ring 100
between the opposing nesting profiles 98. Metallic rings 102 provide the
needed "v" ring nesting profile to support the last ring of the nesting
profile 98. When the valve assembly 24 is positioned in the mandrel
pocket, the packing seal 44 is designed to form a seal between the inner
wall of the mandrel pocket and the outer wall of the valve body 34.
Disposed within the valve body 34 is a cam 104. A cam is a rotating or
sliding piece of any prescribed shape, or a projection of definite shape,
such as on a wheel, either for imparting desired peculiar movement to a
roller moving against its edge, to a pin free to move in a groove on its
face, etc., or for receiving motion from such a roller, pin, etc. The cam
104, in a preferred embodiment, is a cylindrical sleeve member having
first and second opposing ends 106,108. The cam 104 loosely circumscribes
a portion of the tapered intermediate section 84 and is free floating and
thus rotatable about the intermediate section 84. The cam 104 is rotatably
held in position around the tapered intermediate section 84 between the
cam shoulder 86 and the first end portion 76 of the differential piston
assembly 70 and functions within the control fluid chamber 96. Thrust
washers 110 are positioned on opposite ends of the cam 104 to reduce end
to end friction. While the cam 104 is securely held in correct axial
position in the manner just described, there is sufficient clearance
between the outer wall of the cam 104 and the inner wall of the vale body
34 to allow the cam 104 to be free floating and thus rotatable about the
intermediate section 84 of the differential piston assembly 70.
As will be later described in more detail, the cam 104 preferably has a
plurality of interconnected pathways 112 spanning its circumference and
together functioning as a camming surface. While the pathways 112
preferably form an interconnected zigzag pattern, it is appreciated that
the pathways 112 may have a myriad of designs and configurations,
depending on the engineering requirements of any given application. A
follower 114, such as a guide lug, preferably extends from the interior
wall of the valve body 34 into one of the plurality of pathways 112. The
follower 114 effectively couples the cam 104 to the valve body 34 and
causes the cam 104 to be rotatably indexed about the differential piston
assembly 70 when the differential piston assembly 70 is reciprocated
axially. An alternate embodiment may include a track and following device
that follows a prescribed path to translate reciprocating axial movement
of the piston assembly 70 to set the valve stem 68 at a predetermined
axial position or displacement.
A body valve spring 116 is contained within the valve body 34 and is biased
against the end of the valve stem 68. The body valve spring 116 is
designed to overcome the control fluid static pressure head such that when
applied control fluid pressure is not supplied to the body valve 34, the
body valve spring 116 will be able to bias the valve stem 68 to a closed
position even with the pressure head exerting a force toward the open
position.
Turning now to FIG. 3C, the body valve spring 116 extends to just adjacent
a tapered valve stem head assembly 118. Immediately adjacent the end of
the body valve spring 116 is a spring adjusting nut 120 that allows the
tension of the body valve spring 116 to be adjusted as conditions require,
and immediately adjacent the spring adjusting nut 120 is a spring locking
nut 122 that prevents the spring adjusting nut 120 from changing position
through vibrational rotation. Threadedly attached to the end of the
actuator mandrel 72 is a valve stem head collar 124 that is attached to a
tapered valve stem head 126. Adjacent the end of the valve stem head
collar 124 is a threaded lock nut 128 that secures the valve stem head 126
in a set position. However, if so desired, the threaded lock nut 128 may
be positioned to allow the valve stem head 126 to be adjusted to alter the
axial setting of the cam 104. (FIG. 3B). The valve stem head 126 is shown
in the closed position and engaged against the valve seat 130. While a
tapered valve stem head and square-shouldered valve seat have been
illustrated, it will, of course, be appreciated that other types of valves
and seat valve configurations can be utilized in the present invention.
Also illustrated in this figure are the casing fluid inlet ports 40 from
the casing that communicate with the interior volume 74 of the valve body
34.
Briefly, FIG. 3D simply illustrates the conventional check valve assembly
36 having tubing fluid outlet ports 38 formed therein. The check valve
assembly 36 is threadedly secured to the end of the valve seat body 131,
and when the valve stem 126 is off-seat, it is in fluid communication with
the interior volume 74 of the valve body 34.
With a preferred embodiment having been described, a preferred method of
its operation will now be discussed with general reference to FIGS. 2, 3
through 3D, 4A through 4C, FIG. 5 and FIG. 6. The production tubing 18,
the mandrel 28, and the control fluid line 30 are run into the casing 20
and set in position in a conventional manner. As previously stated, the
valve assembly 24 is run into the production tubing 18 with a running
tool, such as a wireline using conventional methods. The valve assembly's
24 downward motion is stopped by the no-go shoulder 66 contacting an
opposing shoulder within the mandrel pocket 26. The lock collar 54 and the
no-go shoulder 66 then cooperatively aid to position the valve assembly 24
in the mandrel pocket 26. As the valve assembly 24 is positioned in the
mandrel pocket 26, the packing seals 44 seal against the interior wall of
the pocket mandrel 26 to provide a fluid tight seal therebetween so that
the control fluid can then be flowed into the valve body 34 through the
casing fluid ports 40 without leaking into the production tubing 18. In
effect, the packing seals 44, isolate the casing fluid from the tubing
fluid such that fluids and their associated pressures can communicate only
through the valve body 34.
As the valve assembly 24 is set in the mandrel pocket 26, the valve stem
head 126 may be biased to the closed position by the valve body spring
116. To unseat the valve stem head 126, the cam 104 is reciprocated and
indexed to achieve the desired orifice setting. As mentioned above, the
cam 104 is a cylindrical sleeve a pattern of pathways 112 spanning its
circumference, which may vary in design depending on the application.
Preferably, the pathways 112 form a zigzag pattern. A representative
zigzag pattern 132 is illustrated in FIGS. 5 and 6 to which specific
reference is now made. More preferably, the zigzag pattern 132 is
preferably a J-slot configuration spanning the circumference of the cam
104 as illustrated in FIGS. 5 and 6. The J-slot is adapted to receive the
follower 114 therein to govern the relative axial position of the valve
stem 68 with respect to the valve body 34.
The pathways 112 of the J-slot configuration are comprised of a series of
offset index paths 134 of varying length and intermediate stop paths 136
interconnected by angled indexing paths 138. The series of off-set stop
paths 136 provide an axial stop position for the follower 114 when the
control fluid pressure is applied, and the off-set index paths 134, which
varying in length, provide an axial index position for the follower 114
when the control fluid pressure is relieved. The longer index paths 134
are designed to incrementally place the valve stem 68 in a selected axial
position relative to the follower 114 when valve stem 68 is shifted
axially with respect to the follower 114. The J-slot configuration can be
configured to achieve a myriad of orifice size openings and may be
aperiodic, if so desired that is they do not necessarily have to achieve
orifice sizes represented by even number values. The size of the orifice
depends on the length of the index path 134 as will now be further
explained.
The follower 114 is initially positioned in the closed position path 140,
which allows the body valve spring 116 to bias the valve stem 68, and
thus, the valve stem head 126 to a closed position as illustrated in FIG.
4A. As control fluid pressure is applied through the control fluid line 30
from a remote location and into the control fluid chamber 96, the fluid
pressure acts on the first seal 90 and second seal 94 around the
differential piston assembly 70. However, since the first seal 90 has the
greater surface area, the force acting on seal 90 is greater than on seal
94 and a lifting force is created with respect to the valve stem 68 and
valve stem head 126. As the control fluid pressure is increased, the lift
force overcomes the resistance provided by the body valve spring 116 and
drives the differential piston assembly 70, the valve stem 68 and the
valve stem head 126 to a fully open position, as illustrated in FIG. 4B.
Since the cam 104 is coupled to the differential piston assembly 70 in the
manner previously described, the cam 104 also moves in the same direction
as the differential piston assembly 70.
As the cam 104 moves, the follower 114 traverses its initial closed path
140 (FIG. 6) until it engages a first angled surface 142. As the first
angled surface 142 is engaged, the follower's 114 angle of incidence on
the first angled surface 142 causes the cam 104 to rotate with respect to
the valve body 34 until the follower 114 is positioned in a cocked
position within a first stop pathway 144 (FIG. 6). In a preferred
embodiment, the rotational direction of the cam 104 is clockwise, however,
it will of course be appreciated that the design could be configured to
rotate in a counterclockwise direction.
When the control fluid pressure is relieved at the remote location, the
control fluid pressure is abated in the control fluid chamber 96. With a
substantial control fluid pressure no longer present, the body valve
spring 116 then forces the valve stem 68 and the cam 104 toward the closed
position. As the cam 104 moves in this manner, the follower 114 then
engages a second angled surface 146 (FIG. 6). The follower's 114 angle of
incidence on the second angled surface 146 causes the cam 104 to rotate,
which engages the follower 114 to a first index path 148. The follower 114
encounters the end of the first index path 148, and this position is held
by the biasing force exerted against the valve stem 68 by the body valve
spring 116. The first index path 148 has a shorter length than the initial
path 140, which axially adjusts the valve stem 68 away from the valve seat
130 and thus leaves the valve stem head 126 unseated and in a partial open
position as illustrated in FIG. 4C.
When the control fluid pressure is again applied, the valve stem 68 and the
cam 104 reciprocate toward a fully open position which causes the follower
114 to track from the first index path 148 toward a third angled surface
150. The follower's 114 angle of incidence rotates the cam 104
sufficiently to cause the follower 114 to traverse to a second stop
position 152. When the control fluid pressure is relieved, the cam 104
reciprocates and causes the follower 114 to track toward and engage a
fourth angled surface 154. The follower's 114 angle of incidence rotates
the cam 104 sufficiently to cause the follower 114 to traverse a second
index path 156. The follower 114 encounters the end of the second index
path 156, and this position is maintained by the force exerted against the
valve stem 68 by the valve body spring 116. The second index path 156 has
a shorter length than the first index path 148, which causes the orifice
to be larger than the orifice corresponding to the first index position
148.
The cam 104 can be indexed in this same manner to a third index position
158 or more positions, depending on the design of the cam 104 until the
cam 104 has made a complete revolution to return the follower 114 to its
initial closed position 140. Each index path 134 that the follower 114
rests in increases the size of the orifice. Thus, the size of the orifice
can be precisely controlled from a remote location via the utilization of
a control fluid.
Another preferred embodiment of valve assembly of the present invention is
illustrated in FIGS. 3E through 3H and FIGS. 4D. The valve assembly 24
represented in these figures is identical to the valve assembly 24
previously discussed above and illustrated in FIGS. 3 through 3D with one
difference. That difference is that the differential piston assembly 70
and a portion of the length of the valve stem 68 have a compensation
pressure port 160 extending therethrough. As illustrated, the compensation
pressure port 160 has a first opening 162 that opens outwardly into the
chamber 88 and extends through the differential piston assembly 70 and a
portion of the length of the actuator mandrel 72. The compensation
pressure port 160 also has a second opening 164 that opens into the hollow
portion of the interior volume 74 of the valve body 34. This places the
chamber 88 and the interior volume 74 of the valve body 34 in fluid
communication with each other. It should be noted that a thread pressure
plug 166 blocks fluid communication between the chamber 88 and the tubing
fluid outlet port 38. Thus, the differential piston assembly 70 in this
particular embodiment is no longer suspectable to the pressure exerted by
the fluid in the tubing. In situations where there is a high pressure
differential between the casing and tubing, this could be a significant
advantage in the efficient operation of the valve.
Reference will now be made to FIGS. 4A through 4D. In the previous
embodiment as illustrated in FIGS. 4A through 4C, there are several forces
involved. First, the chamber 88 is open to the tubing, which exerts a
downward force on the first end portion of the differential piston
assembly 70. Second, there is the valve body spring 116 that is exerting a
force on the valve stem 68 toward the closed position. Third, the
hydrostatic pressure from the control fluid exerts an upward force on the
differential piston assembly 70 toward an open position. Fourth, the
casing pressure exerts a upward force on the second end portion 82 of the
differential piston assembly 70. As long as the difference between the
forces generated by the tubing pressure and casing pressure acting on the
piston assembly 70 is within prescribed limits, the valve functions
properly. However, in those instances where the casing pressure becomes
much greater than the tubing pressure, and particularly if the casing
pressure is also lower than the hydrostatic pressure in the fluid control
conduit, then these differentials can prevent the valve stem 68 from
working properly. If the casing to tubing differential pressure is great
enough, it may prevent the valve from indexing properly. To index the
mechanism fully, the forces working to stroke the valve stem 68 must
overcome those forces resisting. As seen in FIGS. 4A through 4C, the
pressure in the hydraulic line times the difference in area of the first
end and second end portions 76 and 82 of the differential piston assembly
70 must be greater than the sum of the effects of: the body valve spring
force, tubing pressure acting on the first end portion 76, casing pressure
acting on the second end portion 82, friction of the device, and if the
valve is on valve seat 130, the tubing/casing pressure difference times
the area of the valve seat. To complete the indexing cycle, the forces
biasing the valve stem 68 back toward the valve seat 130 must prevail once
the control fluid pressure applied at the remote location is removed. In
applications in which casing pressure is significantly greater than tubing
pressure, the valve illustrated in FIGS. 4A-4C may be inadequate to
prevent the valve stem 68 from floating in the valve body 34 and therefore
changing the orifice size. On the other hand, if tubing pressure becomes
significantly larger than the casing pressure, the control fluid may not
be able to overcome the excessive pressure exerted by the tubing pressure,
thereby causing the valve to malfunction.
However, in the embodiment illustrated in FIG. 4D, the first end portion 76
of the differential piston assembly 70 is not subject to the tubing
pressure and the valve body 34 and the valve stem 68 define a compensation
pressure chamber at an end distal to the process fluid outlet wherein the
valve stem 68 includes a compensation pressure port 160 allowing fluid
communication between the compensation pressure chamber 88 and the
interior of the valve body 34, which is open to the casing pressure. In
such applications, casing pressure may be introduced into the compensation
pressure chamber 88 via the compensation pressure port 160 to nullify any
sensitivity whatsoever to the pressure differential between tubing and
casing. The nullification comes from the casing pressure's ability to
exert a downward force on the larger surface area of the first end portion
76 of the differential piston assembly 70.
Turning now to FIG. 4E, there is yet another embodiment of the valve of the
present invention that may include a tubing pressure transducer 168 or a
valve stem axial displacement transducer 170 for relaying data concerning
the valve to a remote location. With respect to these measuring devices, a
significant advantage of this aspect of the present invention is that it
is highly desirable in downhole flow control valve systems to have an
accurate system for monitoring not only the orifice size of the valve but
the pressure of the production tubing to obtain desired production
parameters within the well. For example, it is advantageous to select a
particular bottom hole pressure and then control the size of the orifice
of the valve to obtain that selected value of bottom hole pressure. Such
systems require a reliable means for both sending data uphole from the
vicinity of the valve as well as processing that data and then actively
controlling the size of the flow control orifice of the valve to obtain
the desired results, as monitored by the system.
In this preferred embodiment, the valve provides transducers for sensing
the displacement of the valve stem (and hence orifice size) and the tubing
pressure. Of course, other sensors, such as a flow rate transducer, are
within the broad scope of the present invention.
From the above, it is apparent that the present invention provides a
remotely-adjustable valve employable in an enhanced-lift recovery system
and a method of adjusting the same. The valve comprises: (1) an elongated
valve body having a process fluid inlet and a process fluid outlet, (2) an
elongated valve stem disposed within the valve body for axial displacement
relative thereto to adjust a rate of process fluid flow between the fluid
inlet and the fluid outlet as a function of a relative axial position of
the valve stem with respect to the valve body and (3) a cam disposed
within the valve body and coupling the valve body and the valve stem, the
cam providing a plurality of axial displacement positions thereon to place
the valve stem at a selected one of a plurality of relative axial
positions with respect to the valve body, the valve body having a control
fluid pressure port for allowing a control fluid pressure to be introduced
into and released from the valve to reciprocate the valve stem axially
with respect to the valve body between cocked and set positions, the cam
moving from a first axial displacement position to a second axial
displacement position as the valve stem is reciprocated, a difference
between the first and second axial displacement positions thereby causing
an adjustment of the rate of process fluid flow between the fluid inlet
and the fluid outlet.
Although the present invention and its advantages have been described in
detail, those skilled in the art should understand that they can make
various changes, substitutions and alterations herein without departing
from the spirit and scope of the invention in its broadest form.
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